Kevin Weeks, 57, who once was protégé of James "Whitey" Bulger described to US District Court jury today modus operandi of the criminal empire ran by Bulger.

Weeks' cooperation with the authorities has led investigators to the graves of three of Bulger's alleged victims in 2000.

Kevin Weeks took the stand wearing a grey T-shirt and black blazer. He told the jury how for 20 years he, James Bulger and Steve Flemmi were part of a criminal enterprise that made million from "extortions, drug dealing, gambling, whatever..."

But it was Weeks recounting of the 1996 murder of Edward Brian Halloran and Michael Donahue that has the courtroom gripped. Halloran was targeted for cooperating with the FBI against Bulger. Donahue, father of three, was an innocent victim just giving a friend a ride home.

"Shakes my entire family," said a family member. "And then what? And then they go and have bite to eat right after it happened? They had just murdered two people. Like it was nothing."

Weeks said Bulger called out to Halloran and they started shooting up Donayoo car. Halloran survived the initial ambush and walked out of the car.

"Bulger started shooting at him," Weeks said. "His body was bouncing off the ground."

The next day, Weeks said, he Bulger and Flemmi went to the tow lot to look at the shoot-out car.

Weeks also described the murder of Arthur "Bucky" Barrett, who Bulger allegedly shot in the head in 1983.

According to Boston.com, Barrett was a safecracker and thief who was involved in the $1 million-plus, 1980 Memorial Day weekend burglary of Depositors Trust bank in Medford. Bulger wanted to shake down Barrett for money, but believed Barrett received protection from the Mafia, Weeks said.

Weeks pleaded guilty in 2000 to racketeering charges, including assisting Bulger in five murders. He served less than six years in exchange for his testimony and for leading investigators to burial sites and dozens of weapons the criminal enterprise possessed.